Wind motor



1931- G. .1. M. DARRIEUS i,820,529

WIND MOTOR Filed June 22, 1928 Patented Aug. 25, 1931 UNITED. STATES PATENT, o FFicET-jJ."

enonens JEAN MARIE DARBIEUS, or PAR-IS, FRANCE, ASSIGNOR 'ro soorn'rn ANQNYME POUR LEXPLOITATION nus ,PROCEDES MAURICE LEBLANC-VICKERS, or A IS,

FRANCE 1 WIVND MOTOR Application filed June 22,1928, Serial No. 287,520, and in France June 2?,1927.

Thisinvention relates to fluid motors and ifnore particularly v to propeller blades. thereor. V

The use of a fluid such asthe Wind for the production of electric energy involves many problems. Theideal for which all have been striving is apparatus therefor having completely automatic operation, and in which,

successful operation is not hindered by needless multiplicity of parts. But, one of the difficulties limiting this ideal has arisen from the need of some additional means compeni sating for the resultant increase of speed and torque produced by av high wind velocity.

actuating fluidsuch as the wind for a given days operation is seldom of constant value, and varies between certain high and low limits, it follows that some means must be provided that is sensitive to'thesevariations in the wind velocity and that Will-withhold and resist an increase of speed of the blades or vanes of a fluid motor. Apparatus has been designed for this purpose.

1 Some have providedan impeller having propeller. blades, vane wheels or thelike, with a tail vane or auxiliary directing vane Wheel pivoted thereto. pellers, the blades or vane wheel were, themselves, often pivotally positioned so that they could be partially or wholly Withdrawn from the thrust of the wind when its velocity exceededa given amount. This wasaccom: plished by means of springscompressed by the increased thrust ofthe actuating fluid.

Another suggested solution consisted in providing the impeller with auxiliary surfaces thatqWere brought into opposition to i forward thrust of the fluid, as by'means of I one has provided an impeller having rigidly mounted blades, vane wheels or the like, that ofthemselves, without the aid of auxiliary equipment or attachments, compensate for, If and suppress unfavorable results produced In other Words, since the velocity of the For larger size im-- by an increase of fluid velocity above the normal varlations of operation. 1 Y L It has been one object of my invention'to provide an impeller that without the of; auxiliary apparatus, can be designed to automatic-ally operate below a certain predeter-s mined speed.

Another object of to provide an impeller that withoutthe aid of auxiliary apparatus, can be designedto keep Within certain limits of torque even my invention has been 7 thoughthe fluid velocity suddenly increases.

Still another object of my invention has been to provide impeller blades having substantially like angles of incidence alongtheir entire length orradius.

A further object of my invention has been to provide an impeller than can be designed to operate at a substantially constant speed,

and to produce a substantially constant torque, governed by the thrust impressed upon its blades for a givenfluid or Wind Velocity. l

A still further-object ofvmyinvention been'to provide an impellerhaving blades of extreme narrowness but of suitable strength and tangential rigidity. i r Y A still further object of my invention has been to provide a more simple, positive,and eflicient impeller blade. v I

These and many other objects 'ofthis in vention will appear to those skilled inthe art" from the following description "taken in con-- j unctionwith theaccompanying drawings in which: I 7 V M Fig. 1 is a plot of propeller characteristic curves used in the design of my invention.

Fig. 2 is a sideview of a device constructed in accordance with a form of my invention.

Flg. 3 1s aslde view of .a deviceconstructed in accordance wlth another formof my 1nvention. I

Fig. 4 is a perspective view of a further embodiment of my invention. k Fig. 5 is. a sectional View of member 15 on line VV of Fig. 3;'and 1 a Fig. 6 shows sectional views on lines VI-'VI and VIVI (b) of member 29 ofFig.4. J l I Although a preferred form of my inven tion is shown in Fig. 4, yet impellers 10, such as shown in Figs. 2 and 3 may be employed, provided that the requirements of torque, speed, and strength are within certain limits. The impellers shown in Figs. 2 and 3 include aalurality of propeller blades or vanes 11, rigi ly secured to a common axis 13. The acre-foils 12 of the blade 11 overlap each other substantial]. in the direction of the axis 13, so as to provide a light but strong compound girder blade. Structure 14 and braces 15, both stream lined to reduce resistance to forward movement may be provided to strengthen the blade 11. Fig. 5 illustrates the stream line form of the brace 15; and, the structure 14 has a similar stream line sec tion, differing from the brace 15 only in relative width.

But, the preferred form of my invention shown in Fig. 4, is designed to meet substantially all the torque, speed, dimension, and strength requirements of nori'nal field service. The operating basis for these requirements is hereafter set forth.

In cases where the extreme narrowness of the blades would induce fear of an insuflioient strength in the tangential direction, the several acre-foils may be staggered with respect to each other in this tangential direetron so as to constitute a frame of a sort of pylon having a great moment of inertia in all directions and substantially braced with re- Spect to shearing forces (see Fig. 4). The blade 21 in Fig. 4 can be employed in place of the blades 11 of Figs. 2 and 3 in connection with the impeller construction shown. Although any suitable type of impeller and drive mechanism can be employed, yet, it follows that the peculiar construction of the blade 21 needs specific description here.

In the preferred embodiment of a propeller blade 21, to which the principles of my in-' vention are particularly adaptable, a plurality of stream line acre-foils have been provided, each of the acre-foils 22 at one end 24 merges with the others to form the apex of a pylon; from the apex 24, each aerofoil slopes outward towards its :;;upport ing end, where it is rigidly and securely fixed to a common axis 26 in any suitable manner. Fig. 6 shows the stream line construction of the aeroioil 22.

The axis 26 may be provided with slots of relatively shallow depth for receiving each supporting end of the blade 21. In order to reinforce the blade 21, a plurality of shelves or stays 28 are positioned to be clamped between the plurality of aerofoils 22, substantially parallel to the blade axis 26, for tying them together at points along their length. To further reinforce against shearing, centrifugal, twisting and other forces inherent in propeller blade action, oblique tie structure 29 of wire or other suitable material is rigidly secured so as t cross brace one acre-foil 22 with respect to the others of a given blade along the length thereof in a manner shown in Fig. 4:.

The wind motor 10, itself, including the blades 21 and their common axis 26, may be positioned as shown in Figs. 2 and 3, or in any other suitable manner, so that the common axis 26 may rotate about a stationary support 9 or the like and that agenerator or the. like can be positioned to rotate with the axis 26 by the employment of suitable gearing, belt, shaft or the like (not shown) In addition, the vanes or blades of the impeller orwind. mill shown in F 2, 3 and i are inclined in the direction of the flow of the wind or actiiating fluid as indicated by the arrows, so that under the action of centriiiu al force, these vanes or blades being of reiatively thin section, tend to straighten themselves, and thus counterbalance the shearing and twisting YfOfCt-bzj exerted by the wind. I

The wind motor system which is the sub ject of thisinven'tion, is based upon the following technical considerations. Sections finely stream lined and with great transversz-il elongation. employed in aviation have the property that, as long as the angle of incidence with re pect to the chord of the section does not exceed a limit of a few degrees, the thrust of the fluid varies nearly proportional to this angle incidence and moreover remains almost exactly normal or perpendicular, not to the chord of the section, but to the direction of the relative speed. On the contrary, beyond a certain critical angle oi. incidence, the drag or resistance to blade advancement, that is'to say the component of the force oi": the fluid parallel to, but in opposite direction to, the relative speed of the blade section, increase-a rapidly, so that a vector representing the resultant blade actuating thrust, departs slightly towards the chord ofthe blade section, from its normal or pGl'iifilldlClllitI' position with respect to the relative speed. From this instant, the thrust of the blade section and its vector component in any direction Whatever now 1 ireciably depend on nothing except the square of the relative speed of this section with respect tothc speed of its actuating fluid. I The wind motorsystem of: thepr-csent invention includes wings, blades or vanes of very fine section, that is to say, having a very small ratio of drag for a given thrust of the actuating fluid.

Due to this feature, the blades can be very little inclined to'the plane of rotation, that is,-tl1cy can have a very small ratio of pitch to'diam'eter, without a corresponding reduction of the tangential or useful component of the actuating fluid thrust and an increase of the drag. This ratio of pitch to diameter may be 3 ;,'and, the purpose of. employing such a ratio will be explainedjf f v In the present invention it is necessary that the tangential or useful speed of'the' blade should be "maintained at a value hi,r ;her"than the velocityoftheactuating fluid, and, for

the form" bf a blade shown in "Fig. which has beendesigned to meet normal working conditions, the ratio should be substantially to 1. j Inother wordsfthefrat'io of the tangentialfspeed'of the blades to the'absolute velocit of the wind should equal l0 tolj. To acconip ish this it isnecessary toprovide blades ofi very fine, stream line section and havingalri'gh ratio ofsurface sweep to blade surface; this latter ratio. is substantially. pro

portional to the ratio of the tangentialv'eloc} ity to the absolute velocity of the wind. But, the diflicult arises in the design and con-, struction 0 a propeller blade that has the necessary properties strength even though of fine, stream-line section; to accomplish this purpose, the inventor has provided a blade comprising three aerofoilsforrn'ed' into a sortof pylon, asbefore explained,

The ratio of 10 to 1] is employed in order that the relative sped Of the blades will iyt substantially depend upon the velocity of the I actuating fluid Iwithin' the: widest limits of variation of the latter anticipated underno'rg mal operation conditions. :Of" course,the

speed of rotation of 'the blades must: remain substantially constant to ensurethe above condition. But, the latter condition ism aintained, sinc e, a given {increase 'inthe wind ve- 'lOOltY Wlll cause a transcendence of the cr1t1,-"

cal valueof'a chosen werking'angle of'incidence that corresponds to a given maximum thrust of fluidj and this transcendence gives rise to the appearance ofa'n' important drag I as the torque or couple and the power stop increase; and also at'fthis point the stream lines of the actuating fluid are then separated; Thus, it follows, a blade having a suitable angle of ineidence can'fbe provided by keeping the'ratio of surfa e p tQisur-facle of blades at'substa'ntially 10'jt'o 11 This ratio, foundedonthe stream line section" of the blade, lays the foundation fora'high tangenw tial speed of the'blade, "In other words,the ratio of the tangential speed of blade to. ab-

solute velocityof actuating fluid willalso be substantially 1O to'l. Employing the above ratios, it has been found that a suitable angle of incidencehaving a desired poinuwill be provided when the'ratio of blade pitch to di'- ameteristaken as 1 to 3. And. further, in

his choice ofbladesections and of their position along the radius ofthe commona'xis, the H inventor, has taken. sirnilarsections having widths inversely proportional to the relative speed of the blades with respect to theirjactuating fluid; or, after a certain distance'jroni' theaxis of rotation, nearly in inverse proportion to their corresponding radiusjor length,

so that the angleof incidence for each portion ofthe'blade along its entire lengthof radius is kept at 'a substantially 'constantjvalue, and that thetranscendence;thereof caused by a highvelocity' of the actuating fluidwill occur simultaneously along theentire radius or lengthof each blade. This gives to' one of I the edges ofthe blade the shape bolaif the other edge is straight. I Another reason for keeping the ratioot pitch'to diameter of a small value, say 1:3, is, in order that the actuating fluid thrust shall have a relatively largevalue in respect to the drag,"and that the wind motorshaH have a high efliciency. 7 l 1 In Fig. 1 is shown a diagram of hipsof a system soiss'a'and the couple or torque as-ordinants. A set of curves have been plotted, each corresponding to f a certain definite value of the velocity of the Wind.

' The generalp th of each of the curves for so of co-ordinants having angular speed as ab-. 7

a certain velocity of the ;Wind, at first.in

creases for a given increase of angularf ve-i lOCltY of speed of the blades, and then,.de-

creases. This condition follows when the ra tio ofthe' pitch to'the diameter and the ratio of the surfaceof the blades to the 'air surface swept is kept at a veryjsm all value. Accord ingtO the present invention such conditions are chosen solthat all the curves representing a certain value of the vel'ocityfof the wind:

touch each other'alonga-c'ommon envelope theneighborhood of which they are very close together. In mathematical language this result is represented by the'ratio' I Tl;

for the points of contact of these curves with their envelope. ,T represents the torque or couple and "V, the velocity of the actuating fluid,'and d represents the derivative. In

other Words, the curves are chosen so that a straight line, indicatedby.ein Fig. 1, can be drawn through theirpoints of contact, and further, so that thea'ngular speed of each portion of the blade is such that the, equation of wind exceeds a value corresponding to. the

normal working speed of the blade,-the critical angleof incidence is exceeded almost simultaneously at practically all points of the radius or 7 length thereof. 1 Thus, there is a sudden increase of drag that for these sections separates the streamlines at the back of the blade or wing and compensates for the slight increase of thrust. Of course, the sections nearer the axis are more sensitive to an increaseof the velocity ofthe wind owing to their less tangentials eed, but as before explained, the choice of e Width and pitch of the blade portions has onset the effect if thereof upon the chosen critical angle of incidence. Further, still in accordance with the inven tion, another safeguard of constancy of the eed beyond the point of normal working is :3 o tained by giving to the electric generator asuitable characteristic; illustrated as (see Fig. 1) according to which, the resisting cou le or torque will increase more rapidly ast e function of the speed since it does not correspond to the slope e of the envelope at its point of operation. This characteristic crosses the envelope in the direction shown inFig. 1 and may representa synchronous alternator running in parallel on a supply system and therefore at constant speed, or t e shunt characteristic of an asynchronous machine with slight slippage. The invention is not limited to these articular constructions (see Figs. 2, 3 an 4), but extends to any method or combination of known elements of stream line section which, b suitable choice of speed and number of lades, of their relative Width, pitch, etc., produces the rticular characteristics of working whic has heretofore been described.

What I claim is:

1. A fluid motor having a plurality of blades mounted on" a common hub, each of said blades having the form of a pylon of triangular section, said pylon cons sting of three aerofoils rigidly secured to the hub.

2. A fluid motor substantially as specified in claim 1' whose blades are bent in the direction of flow of the actuating fluid, so that the centrifugal force of the blades of said motor when rotating will tend to counterbalance the shearing and twisting forces exerted by the actuating fluid.

3. The combination in a fluid motor of a rotating hub, a plurality of radially extending blades of tapered profile rigidly mounted on said hub, said blades being formed so that the pitch at every point of the radius thereof the said blades, so that the tangential speed of said blades will be greater than the velocity of the actuating fluid.

including aplurality-of areofoils rigidly 23;

secured to thehub, the surface area of said aerofoils of the blades having a ratio of not more than 1 to to the area'sweptout b said aerofoils during rotation of the bl a'des,so that a high ratio of tangential speed of the blades to the velocity of the actuating fluid will be maintained.

7. A fluid motor having a rotating hub and a 'plurality 'of blades mounted thereon,

each of said blades having the form of a 1'? p lon of triangulargsection, said-pylon inc uding a gluralityof aerofoils rigidly cured to, t e hub, stays disposed between said aerofoilsfor tying them together at: portions alongtheir length, and oblique ties L j;

for cross bracing one acro foil. withrespect to each of the others along the length of each of said blades. A a I 8. Ina fluid motor the combination of a plurality ofblades' mounted on a common 5 hub, each of said bladeshaving the form of a pylon of. triangular section, said pylon including three aerofoils rigidly secured to the'hub, each of said aerofoils having a pitch which decreases, and a width which decreases with portions of increasing distance from the hub thereof, so thatrbladcs,

will be eprovidedlhaving .a certain definite critical angle ofincldence upon the transcendence of which the stream; lines of, the

actuating fluid will be separated for pro-- venting further increaseof the rotative speed of the blades, and so thatthe vangle of incidence will be. transcended simultaneously along the entire length of the blades,

9. A fluid motor having a plurality 5r bladesmounted on a; common ub,.each of said blades havingthe form of a pylon of trian 'ular section, said pylon including plural ub and merging atone end to form a co n monaex." v

10. fluid motor having a plurality of blades mounted on a common hub,.--each of ity of aerofoils rigidly secured tothe J said blades having the form of apylon of 1 f triangular section, said, pylon. including a plurality of aerofoils rigidly securedto thev hub and oblique ties for crossvbracing one aerofoil with respect to each of the others along the length of'each of said blades, 11. A fluidmotor having a plurality of blades mounted on a common hub, each of said blades having the form of a pylon of triangular section, said pylon including a plurality of areofoils rigidly secured to the hub, stays disposed between said aerofoils for tying them together at portions along their length.

In testimony whereof I have signed my name to this. specification at Paris, France, this 8th day of J une. 1928.

GEORGES JEAN MARIE DARRIEUS. j 

